Typewriter desk



Aug. 2, 1955 c. M. ABRAHAMsoN TYPEWRITER DESK INVENToR J'f/Y.'

Filed NOV. 29, 1951 .l l I Il" TYPEWRITER DESK 6 Sheets-Sheet 2 FiledNOV. 29, 1951 Aug. 2, 1955 c. M. ABRAHAMSQN 2,714,545

TYPEWRITER DESK Filed NOV. 29, 1951 6 Sheets-Sheet 5 6 Sheets-Sheet 4INVENTOR.

"lL/mii TIl-Hhl c. M. ABRAHAMsoN TYPEWRITER DESK Aug. 2, 1955 Filed Nov.29, 1951 [Il-UHU:

Aug. 2, 1955 c. M. ABRAHAMSON TYPEWRITER DESK 6 Sheets-Sheet 5 FiledNov. 29, 1951 Aug. 2, 1955 c. M. ABRAHAMSON 2,714,545

TYPEWRITER DESK Filed Nov. 29, 1951 6 Sheets-Sheet 6 IN VEN TOR.

Affi

TYPiEWRiTER DESK Charles M. Abrahamson, Aurora, Iii., assigner to All-Steel Equipment Inc., a corporation of Iilinois Application November 29,1951, Serial No. 258,953

18 Claims. (Cl. S12- 29) The present invention relates to secretarialdesks of the type provided with a disappearing typewriter compartmenthaving means associated therewith for transferring the typewriter from astored out-of-the-way, concealed position to an extended position foruse.

More specifically the invention relates to a secretarial pedestal deskhaving an end pedestal providing an interior typewriter compartmenthaving associated therewith a slidable carriage which is movable from aretracted position within the compartment to an extended positionforwardly of the pedestal at one side of the desk, and

having mounted thereon a typewriter-supporting shelf which is pivotedadjacent its back or rear edge to the carriage for swinging movementabout a horizontal axis between a horizontal position for use in frontof the pedestal and a vertical out-of-the-way position of alignf shelfbe associated with a stationary support. Accordingly, it is broadly anobject of the invention to provide a novel type of counterbalancingmechanism for drop shelves of the type outlined above in which thevarying gravitational torque applied to the drop shelf and thetypewriter or other supported mass thereon, by virtue of the shifting ofthe center of gravity of the combined mass toward or away from thevertical plane passing through the axis of swinging movement of the dropshelf when moving the latter between its extreme positions, is

etiectively compensated for so that a more or less uni- 1 form yieldingmovement of the drop shelf in either direction throughout its entirerange will result during manual shifting thereof.

The invention, in another aspect thereof is concerned with the centeringor alignment of the extended drop shelf relative to the fore and aftdirection of the desk and the prevention of shifting of the shelf afterthe same has attained its position of use. Accordingly, it is anotherobject of the invention to provide a novel form of cooperatinginterlocking means between the drop shelf and the desk pedestal foraligning the shelf and holding the same securely in its extendedposition for use against lateral or angular shifting.

Yet another aspect of the invention, in a secretarial desk of thecharacter outlined above, relates to a novel means for latching the dropshelf in either its lowered out-of-the-way position or in its elevatedextended position of use. Accordingly, further objects of the inventionare, in the former instance, to provide a novel form of cooperatinglatching mechanism on the drop shelf and ou the supporting carriagetherefor for releasably maintaining the drop shelf in its lower positionice Patented Aug. 2, E95

against the impelling action of the counterbalancing mechanism for thedrop shelf, and in the latter instance, to provide a novel form ofcooperating latching mechanism between the drop shelf and one side ofthe pedestal door opening for releasably maintaining the drop shelf inits elevated position of use.

Yet another object of the invention, in a desk of this character, is toprovide a pedestal desk having a retractable drop shelf,typewriter-supporting, disappear ing carriage which is movable into andout of the typewriter compartment through the door opening thereof,together with novel means for anchoring the hinged compartment door tothe carriage when the latter is extended to prevent undesired movementof the open door as well as to lend a degree of rigidity to the extendedcarriage.

Other objects and advantages of the invention, not at this timeenumerated, will become more readily apparent as the nature of theinvention is better understood.

In the accompanying six sheets of drawings forming a part of thisspecification, one embodiment of the invention has been shown. In thesedrawings:

Fig. l is a perspective view of a pedestal desk constructed inaccordance with the principles of the present invention and providedwith a typewriter compartment having a retractable drop shelfconstruction associated therewith. In this view the drop shelf is shownin an extended position for use with a typewriter mounted thereon.

Fig. 2 is an enlarged fragmentary detail perspective view of one end ofthe desk showing the drop shelf in its lowered but extended position. Inthis View, the desk top has been removed to more clearly reveal the dropshelf supporting instrumentalities.

Fig. 3 is a fragmentary perspective view of one end of the desk takenfrom a location in front of and somewhat below the typewritercompartment. In this View, the typewriter supporting drop shelf is shownextended in its position of use.

Fig. 4 is an enlarged fragmentary front elevational view of an end ofthe desk looking directly into the typewriter compartment and showingthe typewriter supporting drop shelf in its lowered but extendedposition. In this view certain parts have been broken away and otherparts sectioned to more clearly reveal the nature of the invention.

Fig. 5 is a sectional View taken substantially along the line 5 5 ofFig. 4.

Fig. 6 is a sectional view taken substantially along the line 6 6 ofFig. 5.

Fig. 7 is a sectional View taken substantially along the plane indicatedby the line '7-7 of Fig. 3 in the direction of the arrows, but with thedrop shelf in its lowered position.

Fig. 8 is a sectional view taken substantially along the plane indicatedby the line 8-8 of Fig. 3 in the direction of the arrows.

Figs. 9, 10, 1l, l2 and 13 are detailed fragmentary side elevationalviews of the drop shelf counterbalancing mechanism employed inconnection with the present invention and showing the same inprogressively extended positions.

In all of the above described views, similar reference characters areemployed to designate similar parts throughout.

Referring now to the drawings in detail, and particularly to Fig, 1, theimproved drop shelf construction comprising the present invention isshown as being applied to a secretarial typewriter desk of the pedestaltype in which the typewriter, when not in use, is concealed in apedestal at one end of the desk. Pedestal desks of this character arecommonly provided with a second pedestal at the opposite end of the deskfor containing ofce supplies, such as stationery, the opening betweenthe pedestals affording knee room for the typist when the desk top isbeing used as a work space. It is to be distinctly understood, however,that the invention is not limited to use in connection with pedestaldesks, and the same may be applied to other types of office desks orfurniture having a typewriter compartment therein capable ofaccommodating the present drop shelf construction.

The pedestal desk of Fig. l involves in its general organization a desktop 1i) supported by end pedestals 12 and 14 which are spaced apart toprovide a clearance 16 affording knee room for the typist. The pedestal12 is adapted to contain a bank of drawers 17. The pedestal 14 isadapted to enclose an internal typewriter compartment 18 within whichthe desk typewriter T is adapted to be stored in an out-of-the-wayposition when not in use. The compartment 18 is provided with an openfront adapted to 'De closed with a hinged door panel 20 when thetypewriter is in its stored position, a pair of offset hinge assemblies21 (Fig. 3) being provided for supporting the door. A pair of supportingfeet or pontoons 22 and 24 in the form of elongated channel-like memberscarry the entire weight of the desk including the pedestals 12 and 14and serve to maintain the latter elevated from the door.

The typewriter T is adapted to be positioned upon and carried by aretaining shelf or support 26 associated with the pedestal 14, and thepresent invention is directed, in the main, to the mechanism whereby thesupporting shelf 26 is supported by the pedestal 14 for movement betweenan extended position of use and a retracted position wherein the shelfand typewriter supported thereon is wholly enclosed within thecompartment 18 in an out-of-the-way position.

In the form of pedestal desk illustrated, the desk shelf or support 26is of the drop leat` or drop shelf type, which is to say, it assumes ahorizontal elevated position in front of the pedestal 14 at one end ofthe desk when extended for use, as shown in Fig. l, and it assumes aVertical lowered position within the compartment 18 when retracted.During the transition period, while the drop shelf 26 is being movedfrom its extended to its retracted position, the shelf will assume asubstantially vertical position shown in Fig. 2 wherein it is forward ofthe compartment prior to being slid rearwardly thereinto upon thesupporting carriage provided for it, and the nature and function ofwhich will be set forth presently.

Reference to the rear edge of the desk shelf 26 and subsequentreferences to other portions thereof are absolute with respect to theshelf per se in relation to the normal position of the typewriter T whenmounted thereon, while reference to portions of the desk structure otherthan the desk shelf are absolute with respect to the desk considered asa whole. Thus, the rear edge of the desk shelf is actually the left handside edge of the shelf as viewed relative to the desk in Figure l.

Referring now to Figs. l, 2 and 4, the pedestal 14 of the desk includesouter and inner side walls 28 and 30 which are turned inwardly alongtheir front edges as at 32 and 34 to provide a covering for a pair ofcorner frame posts 36 and 38, respectively. A lintel panel 40 extendsacross the upper ends of the posts 36 and 38, and a door sill beam 42likewise extends between the posts at the bottom of the compartment 18.The posts 36 and 38 and beams 4t) and 42 define therebetween therectangular door opening of the compartment 18. The lintel beam 4i)constitutes part of a shelf aligning or centering mechanism, the natureand function of which willv be set forth presently. The pedestal 14 isalso provided with a rear wall 43 and a bottom wall 44.

A gusset plate 45 at the upper right corner of the door opening (Fig. 8)carries a bumper pad 46 for the door 20 and a similar plate and bumperpad 48 and 50,

respectively, are provided at the lower right-hand corner of the dooropening, as shown in Fig. 3.

A front rectangular frame 52 (Fig. 2) including top and bottom members54 and 56, respectively, and side members 58 and 60 is secured withinthe compartment 18 adjacent the front opening thereof. A similar frame62 (Figs. 4 and 7) is secured within the compartment 18 adjacent therear wall thereof and includes top and bottom members 64 and 66 and sidemembers, one of which is shown at 68. The frame members 52 and 62 aresuitably secured to the side walls of the pedestal 14, as by welding.

The vertical side members 58 and 68 of the frame members 52 and 62,respectively, constitute a rigid support for a pair of guide channelsincluding an upper channel (Figs. 2 and 4) and a lower channel 72 withthe channels extending along the side wall 28 of the pedestal 14 insidethe compartment 18. The guide channels 70 and 72 are spaced from thepedestal side wall 28 a distance equal to the width of the frame members58 and 68.

The guide channels 70 and 72 are provided for the purpose of slidablysupporting thereon a horizontally slidab.e carriage designated in itsentirety at 74, and best illustrated in Fig. 3. The carriage 74 is inthe form of a vertically disposed, generally flat plate 76 ofrectangular design, except for the provision of a truncated corner 7'7at the lower forward portion thereof. The carriage plate 76 is providedwith a laterally downturned upper edge flange 7S (see also Fig. 2)having its outer edge turned downwardly as at Si?. The plate 76 isformed with a laterally turned lower edge flange 82.

The horizontal slidable carriage 4 has hingedly secured thereto the dropshelf 26 by means of a pair of hinges S1 which are secured Vto thecarriage plate 76 adjacent the front and rear upper corners thereof, andare secured to the underneath side of the drop shelf'26 adjacent theforwardly extending longitudinal edge thereof, as shown in Fig. 3.

The lower guide channel 72 includes a bottom flange 83 (Fig. 4) havingan upturned edge 85 and an upper horizontal flange 87. The upper guidechannel 7i) (Fig. 2) is of wide channel construction and includes a backor trough member 84, a top flange or rail 86 and a bottom flange or rail88 having a downturned flange 96 coextensive therewith. An intermediateangle rail 92 h aving a laterally and upwardly turned flange 94 issecured within the guide channel 70 and is substantially coextensivetherewith.`

The slidable carriage 74 has secured thereto a horizontally extendingchannel 95 (Fig. 4) which is coextensive with the carriage and whichopposes the guide channel 70 when the carriageV is retracted into thecompartment 18. A forward weight-supporting roller 96 mounted on a stud9S supported on the carriage 74 rests upon the horizontal bottom rail 88of the channel 7 i) and serves in a large measure to support thecombined weight ofy the carriage and the typewriter mounted thereon. Asimilar rear roller 10i) (Fig. 2) is mounted on the carriage rearwardlyof the roller 96 in horizontal alignment therewith and bears upwardlyagainst and moves tractiona'lly upon the underneath surface of thehorizontal guide rail 94. This latter roller assimilates the upwardthrust ofy the rear region ofthe carriage occasioned by the weight ofthe typewriter and drop shelf acting down-V wardly on the carriage at apoint forwardly of the weight supporting roller 96 which operates in themanner of a traveling fulcrurn when the typewriter is mounted on thedrop shelf 16 and when the latter is in its lowered verticalv position.In other words, the unbalanced weight of the. carriage, typewriter anddrop shelf assembly about the axis of the roller 96 is assimilated bythe roller 10i)` riding upwardly onV the underneath side of the rail914. A roller 162 carried onl ay horizontal stud 183 adjacent thefrontend of the guide. rail 70 extendsint-o the channelshaped member 95and is adapted to bear against either the upper or the lower horizontalflange of the channel member 95 to assimilate any downward thrust of thecarriage existing by virtue of the entire mass of the carriage, dropshelf and typewriter, or to assimilate any upward thrust exerted on thecarriage, when the typewriter is removed from the drop shelf, existingby virtue of a spring loading counterbalancing mechanism associated withthe drop shelf, and the nature and function of which will be made clearpresently.

The slidable carriage 74 is guided against lateral thrust by means of apair of spaced traveling thrust rollers 194, mounted on studs 196carried on the lower flange of the channel member 95 and a thrust roller163 mounted on a stud 11@ carried on the top rail S6 of the channelmember 70. The roller 1113 is confined between the body of the carriageplate 76 and the downturned flange 8l) formed thereon. At the bottom ofthe carriage a pair of spaced traveling thrust rollers 11@ mounted onthe laterally turned flange 12 of the carriage are confined between thebase of the channel member 72 and the upturned flange 85 thereof. Anaxially lixed roller 112 mounted on the laterally turned flange S7 ofthe channel member "/2 coopcrates with the side of the carriage plate 76to assimilate the side thrust thereof.

As previously stated, the drop shelf 26 is movable relative to thecarriage 7 4 to which it is hingedly secured between the lower positionillustrated in Fig. 4 and the horizontal position illustrated in Fig. 3.The hinge assemblies 81 are secured to the underneath side of the dropshelf at longitudinaliy spaced points which are disposed forwardly fromthe edge 114 of the drop shelf 26 so that, when the drop shelf is in itselevated horizontal position, a portion thereof extending along the edgellt/i may overlie the extended carriage assembly. The upper edge of theopen door 2@ projects above the plane of the drop shelf 26.

Referring now to 3 and 4, means are provided for releasably securing theforward or outer regions of the extended carriage plate 76 to theforward regions of the door panel 2t) in order to lend a degree ofsupport to the outer end of the carriage as well as to hold the doorpanel 2d against indiscriminate swinging movement relative to the dropshelf 26 when the latter is in its extended position of use. Towardthese ends a locating pin 12d (see also Figs. 5 and 6) having anenlarged head 122 is suitably secured to the forward medial region ofthe door 2t? on the inside thereof. A bracket 124 having an offset andbifurcated arm 126 is secured as at 127 to the opposing face of thecarriage plate 76 near the forward region thereof, and the bifurcationsof the arm 126 are adapted to straddle the shank portion of the locatingpin 121i when the carriage is extended to the position shown in Figs. 3and 5. A resilient keeper spring 128 bears against the head 122 of thelocating pin 121i to take up any lost motion which may exist between thehead of the pin and the bifurcated arm 126, thus safeguarding againstside play of the door Ztl when the parts are secured together in themanner described.

As previously stated, the drop shelf 26 is movable relative to thecarriage 74, to which it is hingedly secured, between the positionillustrated in 4 and the position illustrated in Fig. 3. As will befully described subsequently, such movement between these two positionsis accomplished by the compressional or expanding action of a yieldablecounterbalancing spring leverage mechanism, including a spring proper131i, best illustrated in Fig. 4. Provision is also made whereby whenthe drop shelf assumes the lowered and substantially vertical positionshown in Fig. 4, it may be latched securely to the carriage plate 76,and means are further provided whereby when the drop shelf 26 is in itshorizontal extended position of use it may be latched in such position.

The means for latching the drop shelf 26 to the carriage plate 76 isbest illustrated in Figs. 3 and 7 and comprises a dog 132 which issuitably secured, as by welding, to the inner face of the carriage plate76 in the medial rear regions thereof and having a latching shoulder 134and an inclined cam surface 135 formed thereon. A latch housing 136 isriveted or otherwise secured to the underneath face of the drop shelf 26adjacent the inner edge of the shelf and. is provided with a rectangularentrance opening 138 designed for register with and reception of the dog132 therein when the drop shelf 26 is swung to its lowered position, Amovable latch plate 140 having a rectangular slot 142 therein isslidable in the housing 136 and is normally maintained in a potentiallatching position by means of a coil spring 144 secured at one end to abracket 146 carried on the shelf 26 and at the other end to an operatingbar 148 secured to the latch plate 140. The bar 148 eX- tends along theunderneath side of the drop shelf 26 in close proximity thereto to apoint adjacent the forward edge thereof. A supporting bracket 150 servesto guide the forward end of the operating bar 148, and a manuallyengageable trip member 152 is secured to the bar 148 adjacent the freeend thereof to permit tripping of the latch plate and release of thedrop shelf 26 from its latched position. It will be understood that oneedge of the slot 142 provided in the latch plate 14) is adapted to rideoutwardly on the inclined cam surface 135 provided on the latching dog132 to carry the edge of the slot 142 over the end of the shoulder 134and into latching position behind the shoulder under the influence ofthe spring 144 when the drop shelf is forcibly moved to its loweredposition.

The means for latching the drop shelf 26 in its elevated extendedhorizontal position of use is best illustrated in Figs. 3 and 8.

This means includes a latch member 154 pivotally mounted adjacent itslower end on a stndv156 extending horizontally across the frontright-hand corner frame post 3S adjacent the upper regions thereof. Thelatch member 154 is partially concealed within the corner post 38 and isspring pressed as at 15% so as to partially project inwardly of the dooropening through registering slots provided in the post. The inwardlyprojecting portion of the latch member 154 is provided with a shoulder164) designed for latching engagement with an edge portion 162 of thedrop shelf 26 when the latter is in its elevated position. The latchmember 154 is movable from its advanced latching position as shown inFig. 8 to a retracted position within the corner post 34 against theaction of the spring 15S. ln order to move the latch to its retractedposition so that the shoulder 16) thereof may clear the edge 162 of thedrop shelf 26, a latch-retracting linger 164 is secured as at 166 to themedial regions of a lever arm 163 pivoted as at to the underneath sideof the drop shelf 26. The linger 164 normally occupies a positionwherein its end lies in close proximity to the outer edge surface of thelatch 154. A coil spring 172 has one end thereof secured to the latchmember 164 and has its other end anchored to a bracket 174 suitablesecured to the underneath side of the drop shelf 26. A manually operablerelease trip member 178 mounted on a link 186, pivotally connected as at132 to the free end of the lever arm 163, occupies a position adjacentan inner corner of the drop shelf wherein it is conveniently accessiblefor manipulation. Transverse movement of the trip member 178 will impartmovement to the lever 163 and latch releasing finger 164 so that the endof the latter will bear against the latch 154 and move the same to aretracted position wherein the shoulder thereof clears the edge 162 ofthe drop shelf 26 to permit downward swinging movement of the latter toits retracted position. It is obvious that upon movement of the dropshelf from its lowered position to its elevated position that the edge162 of the drop shelf 26 will bear against the forward inclined edge ofthe latch member 7 154 and progressively retracting' the same until suchtime as the edge 162 moves behind the shoulder 160 so that the dropshelf is thus latched in its extended position of use.

The drop shelf 26 as shown in Fig. 3 is in the form of a flat metalmember having downwardly and inwardly turned marginal edges. A pair oflongitudinally extending reinforcing members 184 and 186 extend alongthe underneath side thereof. The width of the typewriter supportingshelf proper is somewhat greater than the width of the door opening ofthe compartment 15;, but the extreme inner regions of the drop shelf areof reduced width so that a small area of the drop shelf projects intothe compartment and provides the latching edge 162 when the drop shelfis in its extended position of use. A handle 183 may be provided at thefor- Ward left-hand corner of the drop shelf 2.6 as viewed in Fig. 1 tofacilitate movement of the carriage 74, together with the pivoted dropshelf 26, into and out of the compartment 18 when the drop shelf is inits lowered position.

In order to align the drop shelf 26 when in its extended horizontalposition, as well as to lend rigidity thereto, a pair of spacedcentering pins 189 carried at the outer edge of a liange 191 formedalong the inner edge of the drop shelf is adapted to enter registeringholes 193 provided in the door lintel panel 4t) and beam 64.. AnL-bracket 192 (Figs. 2 and 8) is secured to the inside face 0f sidemember 58 of frame 52 and a bearing merriber 194 (Figs. 2 and 3) issecured to the rear marginal edge of shelf 26. When the shelf is in itshorizontal position, L-bracket 192 contacts the top of shelf 26, asshown in Fig. 8, while member 194 contacts the rear edge of side member58, as shown in Fig. 3. Entering pins 189 and member 194 will preventsubstantial movement of shelf 26 in a horizontal plane while L-bracket192, member 194, and latch member 154 will prevent substantial movementof shelf 26 in a vertical plane.

The counterbalancing and leverage mechanism for the drop shelf is bestillustrated in Figs. 2, 3 and 4, and its "5i principles of operationhave been illustrated somewhat schematically in Figs. 9 to l2 inclusive.This counterbalancing and leverage mechanism is so designed as to actupon the combined mass of the drop shelf and the applied oliice machineor typewriter during movement of the drop shelf between its retractedand extended positions in such a manner that a more or less constanttension within reasonable limits is maintained for counterbalancingpurposes. The previously mentioned spring 130 constitutes the soleforce-applying means of the counterbalancing and il leverage mechanismand the leverage system associated with the spring is such that when thespring is compressed to the maximum extent of which it is capable withinthe system, the leverage system exerts its least counterbalancing effectupon the drop shelf. when the shelf is in its lowermost position. Whenthe drop shelf assumes its elevated position of use, the tension of thespring 130 may be nearly expended, but at this time the leverage systemassociated therewith exerts its maximum leverage effect upon the dropshelf. The action of the counterbalancing and leverage mechanism ispredicated upon the fact that as the center of mass of the combined dropshelf and typewriter carried thereby shifts laterally outwardly awayfrom the vertical plane of the carriage 76, the moment of torque appliedto the drop shelf assembly due to gravity acting on the center of massincreases progressively. Thus the increments of countertorque which mustbe applied to the drop shelf to just counterbalance the applied torquernust be of an increasing nature so that, in the normal movement of thedrop shelf toward. its elevated position of use, a generally uniformapplication of manual torque to the drop shelf will effect such movementwithout sudden yielding of the drop shelf and without sudden resistanceto motion. An adjustment is.` provided. for the spring 1,30; which mayconven- This condition obtains iently be made to accommodate the varyingweight of different typewriters which may be installed upon the dropshelf, and to provide the desired lift for the drop shelf.

Referring now to Fig. 3, the rear end of the carriage 74 has securedthereto a laterally extending, generally triangular back plate 200 whichprojects transversely of the compartment 18 and which is reinforced atits bottom by means of a triangular gusset plate 202. A lever arm 204 ispivotally secured as at 206 to the back plate 200 adjat cent the lowerleft-hand corner thereof as viewed in Fig. 2,

and projects upwardly and diagonally across the compartment 1S andcarries at its free or swinging end a roller 208. A wedge-shaped bracket210 (Figs. 2, 9 to 13 inclusive) is mounted on the rear or inner edge212 of the drop shelf 26 and carries an elongated channel shape guidemember 214 having inturned retaining flanges 216 and in which channelmember the roller 208 is adapted to travel. The axis of the channelmember 214 extends at a slight incline with respect to the plane of thedrop shelf and the specific angularity of the channel axis is designedaccording to engineering exigencies so that certain principles ofleverage existing between the coil spring 130 and the drop shelf willexist during swinging movement of the drop shelf, all in a manner thatwill become clear presently.

The coil spring 130 is mounted upon a guide rod 218 threadedly receivedin a socket member 220 pivoted as at 221 in a bracket 222 secured to thecarriage plate 76 adjacent the rear lowermost corner thereof. The guiderod 21S projects outwardly through a slot 224 (Fig. 3) provided in thecarriage plate 7 6 and projects through the laterally turned end 226 ofa link 228 secured as at 230 to the medial regions of the lever arm 204.The lower end of the spring 130 is centered within a cup member 232threadedly received on the lower threaded end 234 of the mi. gride rod21S and the upper end thereof bears against a ferrule 236 slidablymounted on the guide rod 218 and bearing against the laterally turnedend 226 of the link 228.

From the above description it will be seen that when the drop shelf 26is in its vertical lowered position illustrated in Figs. 4 and 9, theroller 203 will occupy a position adjacent one end of the channel guidemember 214, which is the upper end thereof. At this time the lever arm204 will assume a position wherein the counterbalancing spring 130 iscompressed to the fullest extent of which it is capable in thearrangement shown. With the parts in the position just described, thespring 130 acting through the link 22S will urge the lever arm 204 toswing in a counterclockwise direction as viewed in Fig. 9 and thus theroller 203 carried at the free swinging end of the lever 204 will beurged upwardly and to the left as viewed in Fig. 9 so as to in turnexert a leverage upon the drop shelf 26 and the mass of the typewritercarried thereon tending to swing the drop shelf in a clockwise directionso as to extend the shelf toward its raised position of use. lnas muchas the drop shelf is in its latched position under the iniiuence of thepreviously described latching mechanism including the latch dog 132 andlatch plate 140, the drop shelf is maintained immobile, however, as soonas the latch mechanism is released in the manner previously described,the leverage exerted by the roller 208 on the drop shelf 26 may takeeffect and swinging movement of the drop shelf upwardly will commence.The extent of this leverage applied by the roller 208 to the drop shelf26 is,

L however, relatively small since the compound leverage system actingthereon consists of two compounded thirdclass lever actions. Such aleverage action conforms to the principles of the present invention inthat the center of gravity of the drop shelf and attached typewriter isf relatively close to the vertical plane of the axis of the hinges 81 ofthe drop shelf 26. The rate of the spring 130 is such that` when it isfully compressed as shown in Fig. 9 with the drop shelf 26 beingsubstantially vertical, the compound third-class lever action exertedupon the drop shelf is just sufficient to overcome the gravitationaltorque applied to the drop Shelf tending to maintain the same in itsvertical position.

In Fig. 10, the drop shelf 26 has been moved to a position wherein itmakes an angle of substantially 30 with the vertical plane of thecarriage plate 76. In this position, the center of gravity of the dropshelf and its attached typewriter has moved outwardly to an extentproportional to the sine of the angle subtended between the planes ofthe drop shelf and the vertical plane of the carriage plate 76 so thatthe gravitational torque applied to the drop shelf is substantiallygreater. To counterbalance this added torque effect, the roller S hasmoved inwardly from the upper end of the channel member 214 a slightdistance so that the compound third-class lever actions applied to thedrop shelf have increased. Due to the fact that lever arm 204 isapproaching a position which is normal to the axis of the guide rod 21S,the rst third-class leverage component of the compound system isslightly increased due to the fact that the roller 20S has moved fartheraway from the axis of the hinges 81. The second leverage component ofthe compound system has also increased. The net result is that theproduct of these two leverage components is materially greater. In thisposition of the drop shelf 26, the rate of the spring 130 and the extentof the leverage action exerted thereby on the drop shelf are again justsufficient to overcome the gravitational torque applied to the shelf andtypewriter assembly so that the tendency of the latter still is to swingupwardly toward the extended position of the drop shelf.

In Figs. 1l and l2 the positions of the various components of theleverage system are illustrated when the drop shelf 26 assumes a 45 anda 60 angle with respect to the vertical plane of the hinge axis. In eachinstance both components of the dual compound thirdclass leverage systemincrease so that the product thereof rapidly increases the torqueapplied to the drop shelf tending to elevate the same. As the drop shelf26 continues to move upwardly, the roller 208 moves farther away fromthe horizontal axis of the hinges 81, thereby increasing the extent ofthe compound leverage action not only to account for the outwardshifting of the center of gravity of the mass of the typewriter and dropshelf, but also to account for the decrease in force applied to the link228 by the progressively expanding compression spring 130. At any givenangular position of the drop shelf 26, the rate of the spring 130 andthe extent of the leverage exerted by the roller 208 on the wall of thechannel member 214 is such as to just overcome the effect ofgravitational torque acting on the drop shelf 26 and the typewritermounted thereon.

In Fig. 13 the drop shelf 26 is illustrated in the position it willassume just prior to becoming horizontal and immediately before the edge162 ofthe shelf (Figs. 3 and 8) trips the latch 154 and moves over theshoulder 160 thereof. In this position of the drop shelf 26, the roller208 has moved to the left-hand end of the channel member 214 as viewedin Fig. 13, so that a relatively powerful compound leverage action,involving the link 228 and lever arm 204 as the irst component andinvolving the roller 204 and channel member 214 as the second component,is exerted on the drop shelf tending to move the same to its iinalhorizontal latched position. Although the force existing in the spring130 may be nearly expended, the extent of the compound leverage actionis such as to move the drop shelf to its inal position against theincreased gravitational torque exerted on the drop shelf and articlecarried thereby. It will be seen that by rotating the cup member 232 onthe threaded portion 234 of the guide rod 218 so as to move the memberaxially along the guide rod 218, the effective rate of the spring 130may be varied to accommodate typewriters having different weights.

The invention is not to be limited to the exact arrangementof partsshown in the accompanying drawings and described in this specieation, asvarious changes in the details of construction may be resorted towithout departing from the spirit of the invention. For example, whilethe improved counterbalancing mechanism of the present invention isshown as being applied to a drop shelf associated with the movablecarriage of a pedestal desk typewriter compartment, the counterbalancingmechanism may be found useful, with or without modication, forcounterbalancing the weight of drop shelves designed to support objectsother than typewriters, as for example sewing machines and machinesother than those designed for office or household use. Thecounterbalancing mechanism may be used in connection with stationarysupports as well as with sliding, disappearing carriages of the typeillustrated herein.. Only insofar as the invention has been particularlypointed out in the accompanying claims is the same to be limited.

I claim:

1. A supporting structure for typewriters and the like comprising asupport, a typewriter-supporting drop shelf pivoted adjacent its rearedge to said support and movable frorn a substantially horizontaloperative position, by a swinging action about a horizontal axis,downwardly to an approximately vertical out-of-the-way lowered position,and instrumentalities for counterbalancing the weight of said drop shelfand the typewriter mounted thereon comprising a member mounted on andmovable bodily with the drop shelf and providing an elongated guidewayextending generally in the fore and aft direction of the drop shelf, alever arm having one end pivoted to said support below the level of thedrop shelf when extended and about an axis spaced forwardly from thevertical plane of the drop shelf when in its out-of-theway position, afollower carried at the free end of said lever arm and conned in saidguideway, and spring means normally urging said lever arm about thepivotal axis thereof in a direction whereby said follower is constrainedto move forwardly in said guideway.

2. A supporting structure for typewriters and the like comprising asupport, a typewriter-supporting drop shelf pivoted adjacent its rearedge to said support and movable from a substantially horizontaloperative position, by a swinging action about a horizontal axis,downwardly to an approximately vertical out-of-the-way lowered position,and instrumentalities for counterbalancing the weight of said drop shelfand the typewriter mounted thereon comprising a member mounted on andmovable bodily with the drop shelf and providing an elongated guidewayextending generally in the fore and aft direction of the drop shelf, alever arm having one end pivoted to said support below the level of thedrop shelf when extended and about an axis spaced forwardly from thevertical plane of the drop shelf when n its out-of-theway position, afollower carried at the free end of said lever arm and conned in saidguideway, and a spring having one end effectively bearing against saidsupport and its other end effectively bearing against said lever arm ata point medially thereof and normally urging said lever arm about thepivotal axis thereof in a direction whereby said follower is constrainedto move forwardly in said guideway.

3. Asupporting structure for typewriters and the like comprising asupport, a typewriter-supperting drop shelf pivoted adjacent its rearedge to said support and movable from a substantially horizontaloperative position, by a swinging action about a horizontal axis,downwardly to an approximately vertical out-of-the-way lowered position,and instrumentalities for counterbalancing the weight of said drop shelfand typewriter mounted thereon comprising a member mounted on andmovable bodily with the drop shelf and providing an elongated guidewayforwardly of said axis and extending generally in a `fore and aftdirection relative to the drop shelf, a lever arm having one end pivotedto said support below the level of the drop shelf when extended andabout an axis spaced forwardly from the vertical plane of the drop shelfwhen in its out-of-the-way position, a follower carried at the free endof said lever arm and confined in said guideway, and spring meansnormally urging said lever arm about the pivotal axis thereof in adirection whereby said follower is constrained to move forwardly in saidguideway.

4. A supporting structure for typewriters and the like v comprising asupport, a typewriter-supporting drop shelf pivoted adjacent its rearedge to said support and movable from a substantially horizontaloperative position, by a swinging action, about a horizontal axis,downwardly to an approximately vertical out-of-the-way lowered position,and instrumentalities for counterbalancing the weight of said drop shelfand typewriter mounted thereon comprising a member mounted on andmovable bodily with the drop shelf and providing an elongated guidewayextending generally in a fore and aft direction relative to the dropshelf, a lever arm having one end pivoted to said support below thelevel of said horizontal axis at a point spaced forwardly from saidaxis, a follower carried at the free end of said lever arm and confinedin said guideway, a spring having one end effectively bearing againstsaid support and its other end effectively bearing against said leverarm at a point medially thereof and normally urging said lever arm aboutthe pivot point thereof in a direction whereby said follower isconstrained to move forwardly in said guideway, and means for varyingthe effective rate of said spring to accommodate the weight of differenttypewriters mounted on said drop shelf.

5. A supporting structure for typewriters and the like comprising asupport, a typewriter-supporting drop shelf pivoted adjacent its rearedge to said support and movable from a substantially horizontaloperative position, by a swinging action about a horizontal axis,downwardly to an approximately vertical out-of-the-way lowered position,and instrumentalities for counterbalancing the weight of said drop shelfand typewriter mounted thereon comprising a member mounted on andmovable l bodily with the drop shelf and providing an elongated guidewayforwardly of said axis and extending generally in a fore and aftdirection relative to the drop shelf, a lever aim having one end pivotedto said support below the level of the drop shelf when extended andabout an axis spaced forwardly from the vertical plane of the drop shelfwhen in its out-of-the-way position, a follower carried at the free endof said lever arm and confined in said guideway, a guide rod pivotallysecured to said support for swinging movement about a horizontal axisadjacent the vertical plane of the drop shelf when in its verticalposition and projecting forwardly therefrom, a thrust member mounted onsaid guide rod adjacent its pivoted end, a compression springsurrounding said guide rod and bearing at one end against said thrustmember and effectively bearing at the other end against said lever armin the medial regions thereof for normally urging said lever arm aboutthe pivotal axis thereof in a direction whereby said follower isconstrained to move forwardly in said guideways.

6, A supporting structure for typewriters and the like comprising asupport, a typewriter-supporting drop shelf pivoted adjacent its rearedge to said support and movable from a substantially horizontaloperative position, by a swinging action about a horizontal axis,downwardly to an approximately vertical out-of-the-way lowered position,and instrumentalities for counterbalmcing the weight of said drop shelfand typewriter mounted thereon comprising an elongated channel membermounted on and movable bodily with the drop shelf and having one endthereof positioned adjacent said horizontal axis and its other endpositioned adjacent the forward edge of the drop shelf, a lever armhaving one end pivoted to said support below the level of the drop shelfwhen extended and forwardly of the vertical plane passing through saidaxis, a follower roller mounted on the free end of said lever arm andconfined in said channel member, the length of said lever arm being suchthat the roller assumes a position within said channel member adjacentone end thereof when the drop shelf is in its vertical lowered positionand adjacent the other end of the channel memberv when the drop shelf isin its horizontal operative position, and spring means normally urgingsaid lever arm in a direction whereby said follower is constrained tomove forwardly in said channel member, said spring mea-ns and lever armbeing constructed and arranged wherebyy the maximum counter-torqueapplied to the drop shelf to overcome the weight of the drop shelf andits load occurs when the drop shelf is adjacent horizontal position.

7. A supporting struc-ture for typewriters and the like comprising asupport, a typewriter-supporting drop shelf pivoted adjacent its rearedge to said support and movable from a substantially horizontaloperative position, by a swinging action about a horizontal. axis,downwardly to an approximately vertical out-of-the-way lowered posiion,and instrumentalities for counterbalancing the weight of said drop shelfand typewriter mounted thereon comprising an elongated channel membermounted on and movable bodily with the drop shelf and having one endthereof positioned adjacent said horizontal axis and its other endpositioned adjacent the forward edge of the drop shelf, a lever armhaving one end pivoted to said support below the level of the drop shelfwhen extended and forwardly of the vertical plane passing through saidaxis, a follower roller mounted on the free end of said lever arm andconfined in said channel member, the length of said lever arm being suchthat the roller assumes a position within said channel member adjacentone end thereof when the drop shelf is in its vertical lowered positionand adjacent the other end of the channel member when the drop. shelf isin its horizontal operative position, and a spring having one endelfectively bearing against said support and its other end bearingagainst said lever arm at a point medially thereof and normally urgingsaid lever arm in a direction whereby said follower is constrained tomove forwardly in said channel member, said spring and lever arm beingconstructed and arranged whereby the maximum counter-.torque applied to.the drop shelf to overcome the weight of the drop shelf and its loadoccurs when. the drop shelf is adjacent horizontal position.

8. A supporting structure for typewriters and the like comprising asupport, a typewriter-supporting drop shelf pivoted adjacent its rearedge to said support and movable from a substantially horizontaloperative position, by a swinging action about` a horizontal: axis,downwardly to an approximately vertical out-of-the-way lowered position,and means for counterbal'ancing the weight of the drop shelf and thetypewriter mounted thereon comprising a compound leverage systemincluding a third-class lever fulcrumed on said support below the dropshelf pivot and having a force4 applying end, means providing a secondthird-class lever fulcrumed about said horizontal axis, saidnfirst leverhaving its force-applying end in slidable engagement with said secondlever to vary the point of application of force from the first lever tothe second lever and yieldable means for applying power to said firstlever.

9. A supportingA structure for typewriters and the like comprisingy asupport, atypewriter-supporting drop shelf pivoted adjacentits rear edgeto said support and movable from a substantially horizontal operativeposition, by a swinging action about ahorizontal axis, downwardly to anapproximately vertical out-of-the-way lowered posi- .,tion, andinstrumentalities for counterbalancing the weight of said drop shelf andtypewriter mounted thereon comprising an elongated channel membermounted on and movable bodily with 'the drop shelf, and having one endthereof positioned" adjacentl said horizontal axis and its other endpositioned adjacent the forward edge of the drop shelf, a lever armhaving one end pivoted to said support below the level of the drop shelfwhen extended and forwardly of the vertical plane passing through axis,a follower roller mounted on the free end of said lever arm and confinedin said channel member, the length of said lever arm being such that theroller assumes a position within said channel member adjacent one endthereof when the drop shelf is in its vertica lowered position andadjacent the other end of the channel member when the drop shelf is in ihorizontal operative position, a guide rod having a t ood end pivotallysecured to said support, a thrust member threadedly received on saidguide rod, a link secured to said lever arm medially thereof and throughwhich said slidably extends and a compression spring sr onnding saidguide rod and bearing at one end again 't "aid thrust member and at theother end against said i mally urging said lever arm about the pif-.fo 1in a direction whereby said roller is constraine forwardly in saidchannel member.

l0. In a device of the character described, a desk provided with apedestal, a carriage slidable in said pedestal between a retractedposition wherein it is wholly contained within the pedestal to anadvanced position wherein it is projected therefrom, a drop shelfpivoted adjacent its rear edge to said carriage and movable from asubstantially horizontal operative position, by a swinging action abouta horizontal axis, downwardly to an approximately verticalout-of-the-way lowered position, and instrumentalities forcounterbalancing the weight of said drop shelf and an article supportedthereon comprising a member mounted on and movable bodily with the dropshelf and providing an elongated guideway extending generally in thefore and aft direction of the shelf, a lever arm having one end pivotedto said carriage below the level of said axis and forwardly thereof, afollower carried at the free end of said lever arm and confined in saidguideway and a spring having one end effectively bearing against saidcarriage and its other end effectively bearing against said lever armmedially thereof and normally urging the latter about the pivotal axisthereof in a direction whereby said follower is constrained to moveforwardly in said guideway, said spring and lever being constructed andarranged whereby the countertorque applied to the drop shelf to overcomethe weight of the drop shelf and its load substantially equals orexceeds the torque of said drop shelf and load at any given angularposition of the drop shelf.

ll, A desk provided with a pedestal having inner and outer side walls, acarriage slidable in said pedestal between a retracted position whereinit is wholly contained within the pedestal and an advanced positionwherein it is projected therefrom, a drop shelf pivotally mountedadjacent its rear edge to the upper regions of said carriage forswinging movement about a horizontal axis from a horizontal position ofuse to a vertical lowered position, instrumentalities forcounterbalancing the weight of said drop shelf and the typewritermounted thereon comprising a lever pivoted to said carriage at one endat a point spaced forwardly from the vertical plane oi the drop shelfwhen in its lowered position and having its other end slidably connectedto the drop shelf, spring means normally urging said lever about itspivot in a direction to cause the other end of said lever to moveforwardly along said drop shelf, said counterbalancing means normallyurging said drop shelf to its horizontal extended position, cooperatingreleasable latch means on said carriage and drop shelf for securing saiddrop shelf in its lowered position, and cooperating releasable latchmeans on said drop shelf and pedestal for securing said drop shelf inits horizontal position.

l2. A typewriter desk having an end pedestal provided with inner andouter side walls and enclosing a type- Writer compartment therein, theforward end of said pedestal being provided with a door openingcommunilll eating with said compartment and having a liutel beam, acarriage comprising a substantially vertical plate slidable horizontallyinto and out of said compartment adjacent the outer side wall of thepedestal, a typewriter supporting drop shelf pivoted adjacent its rearedge to the upper regions of said carriage plate and movable from asubstantially horizontal operative position, by a swinging action abouta horizontal axis, downwardly to an approximately vertical loweredposition, instrumentalities for counterbalancing the weight of said dropshelf with a typewriter mounted thereon, said drop shelf being providedwith a typewriter supporting surface of a width greater than thetransverse width of said door opening and being provided with an endregion of a width less than the width of said door opening, said latterregion of the drop shelf directly underlying said lintel beam when thecarriage is extended and the drop shelf is in its horizontal operativeposition, and cooperating centering means on said lintel beam and theunderlying portion of said drop shelf for aligning said drop shelfrelative to said pedestal in all horizontal directions when the dropshelf is in its horizontal position said cooperating centering meansincluding a tapered pin and a mating opening, one being associated withthe lin'tel beam and the other with said drop shelf.

13. A supporting structure for typewriters and the like comprising asupport, a typewriter-supporting drop shelf pivoted adjacent its rearedge to said support and movable from a substantially horizontaloperative position, by a swinging action about a horizontal axis,downwardly to an approximately vertical out-of-the-way lowered position,and instrumentalities for counterbalancing the weight of said drop shelfand the typewriter mounted thereon comprising a member mounted on andmovable bodily with the drop shelf and providing an elongated guidewayforwardly of said axis and extending generally in the fore and aftdirection of the drop shelf, a lever arm having one end pivoted to saidsupport below the level of the drop shelf when extended and about anaxis spaced forwardly from the vertical plane of the drop shelf when inits out-of-the-way position, a follower carried at the free end of saidlever arm and confined in said guideway, and a spring having one endeffectively bearing against said support and its other end effectivelybearing against said lever arm at a point medially thereof and normallyurging said lever arm about the pivotal axis thereof in a directionwhereby said follower is constrained to move forwardly in said guideway.

14. A supporting structure for typewriters and the like comprising asupport, a typewriter-supporting drop shelf pivoted adjacent its rearedge to said support and movable from a substantially horizontaloperative position, by a swinging action about a horizontal axis,downwardly to an approximately vertical out-of-the-way lowered position,and nstrumentalities for counterbalancing the weight of said drop shelfand the typewriter mounted thereon comprising a lever arm having one endpivoted to said support below the level of the drop shelf when extendedand about an axis spaced forwardly from the vertical plane of the dropshelf when in its out-of-the-way position and having a force applyingend, a member movable bodily with the drop shelf and extending generallyin the fore and aft direction of the drop shelf, said lever arm havingits force-applying end in slidable engagement with said member to varythe point of application of force from the lever arm to said member, anda spring having one end effectively bearing against said lever arm at apoint medially thereof and normally urging said lever arm about thepivotal axis thereof in a direction whereby the force-applying end ofsaid lever arm is constrained to move forwardly along said member.

l5. A supporting structure for typewriters and the like comprising asupport, a typewriter-supporting drop shelf pivoted adjacent its rearedge to said support and movable from a substantially horizontaloperative position, by a swinging action about a horizontal axis,downwardly to an approximately vertical out-of-the-way lowered position,and instrumentalities for counterbalancing the weight of said drop shelfand the typewriter mounted thereon comprising a lever arm having one endpivoted to said support below the level of the drop shelf when extendedand about an axis spaced forwardly from the vertical plane of the dropshelf when in its out-of-the-way position and having a force applyingend, a member movable bodily with the drop shelf and extending generallyin the fore and aft direction of the drop shelf, said lever arm havingits force-applying end in slidable engagement with said member to varythe point of application of force from the lever arm to said member, andspring means normally urging said lever arm about the pivotal axisthereof in a direction whereby the force-applying end of said lever armis constrained to move foi'- Wardly along said member.

16. A supporting structure for typewriters and the like comprising asupport, a typewriter-supporting drop shelf pivoted adjacent its rearedge to said support and movable from a substantially horizontaloperative position, by a swinging action about a horizontal axis,downwardly to an approximately vertical out-of-the-way lowered position,and instrumentalities for counterbalancing the weight of said drop shelfand the typewriter mounted thereon comprising a lever arm having one endpivoted to said support below the level of the drop shelf when extendedand about an axis spaced forwardly from the vertical plane of the dropshelf when in its out-of-theway position and having a force applyingend, a member movabie bodily with the drop shelf and extending generallyin the fore and aft direction of the drop shelf, said lever arm havingits force-applying end in slidable engagement with said member to varythe point of application of force from the lever arm to said member, anda spring having one end effectively bearing against said lever arm atpoint medially thereof and normally urging said lever arm about thepivotal axis thereof in a direction whereby the force-applying end ofsaid lever arm is constrained to'move forwardly along said member, saidspring means and lever arm being constructed and arranged whereby themaximum counter-torque applied to the drop shelf to overcome the weightof the drop shelf and its load occurs when the drop shelf is adjacenthorizontal position.

1.7. A typewriter desk having an end pedestal provided with inner andouter side walls and enclosing a typewriter compartment therein, theforward end of said pedestal being provided with a door openingcommunicating with said compartment and having a lintel beam member, acarriage comprising a substantially vertical plate slidable horizontallyinto and out of said Compartment adiacent the outer side wall of thepedestal, a typewriter supporting drop shelf member pivoted adjacent itsrear edge to the upper regions of said carriage plate and movable from asubstantially horizontal operative position, by swinging action about ahorizontal axis, downwardly to an approximately vertical loweredposition, instrumentalities for counterbalancing the weight of said dropshelf member with typewriter mounted thereon, said drop shelf memberbeing provided with a typewriter supporting surface of c. width greaterthan the transverse width of said door opening and being provided withan end region of a width less than the width of said door opening, saidlatter region of the drop shelf member directly underlying said lintelbeam member when the carriage is extended and the drop shelf niemeer isin its horizontal operative position, and spaced centering pins providedon one of said members and cooperating with spaced holes formed in theother of said members to align said drop shelf member relative to saidpedestal in all horizontal directions when the drop shelf member is inits horizontal position.

1S. A typewriter desk having an end pedestal provided with inner andouter side walls and enclosing a typewriter con' tment therein, theforward end of said pedestal being provided with a door openingcommunicating with said compartment and having a lintel beam, a carriagecomprising a substantially vertical plate slidable horizontaliy into andout of said compartment adjacent the outer side wall of the pedestal, atypewriter supporting drop sheif pivoted adiaceut its rear edge to theupper regions of said carriage plate and movable from a substantiallyhorizontal operative position, by a swinging action about a horizontalaxis, downwardly to an approximately vertical lowered position,instrumentalities for counterbalancing the weight of said drop shelfwith a typewriter nounted thereon, said drop shelf being provided with atypewriter supporting surface of a width greater than the transversewidth of said door opening and being provided with end region of a widthless than the width of said i door opening, said latter region of thedrop shelf directly Y underlying said lintel beam when the carriage isextended and the drop shelf is its horizontal operative position, andspaced centering pins on the underlying portion of said drop shelfcooperating with spaced holes formed in said lintel beam for aligningsaid drop shelf relative to said pedestal in all horizontal directionswhen the drop shelf is in its horizontal position.

References Cited in the file of this patent UNTED STATES PATENTS 490,593Vetter Jan. 24, 1893 1,072,121 Hunter Sept. 2, 1913 1,376,373 Sitto Mar.1, 1921 1,725,816 Miller Aug. 27, 1929 1,941,541 VDibble lan. 2, 19342,173,302 Koch Sept. 19, 1939 2,271,241 Reitzel ian. 27, 1942 2,289,664Link luly 14, 1942 2,311,861 Page Feb. 23, 1943 2,372,718 Fox Apr. 3,1945 2,557,719 Bioomstron Iune 19, 1951

